Flexible exhaust line joint



E. c;. WELLS v FLEXIBLE EXHAUST LINE JOINT Fiied Feb. 16, 1940 IIIIII I Wel'snnen or Patented "Ma 20, 1941 UNITED STATES PATENT OFFICE FLEXIBLE EXHAUST LINE JOINT Edward 0. Wells, Seattle, Wash, assignor to Boeing Aircraft Company, Seattle, Wash., a cor-.

poration of Washington {Application February 16, 1940, Serial No. 319,287

4 Claims. (Cl. 285 92) Aircraft engines are subject to vibration in various directions. vibrates or oscillates principally torsionally about the axis of its crankshaft. Flexible engine in the exhaust gas pressure, and which is therefore always adequate, under all conditions, and without binding, to maintain the joint self-sealing and adequately tight.

It is likewise an object to provide a joint for such uses which, in a pressure conduit, is held tight not only by the pressure difierential be tween the gas coursing through it and the lower exterior pressure, but which is further held tightly by'a pressure increase effective especially at thejoint, dueto a reverse Venturi efiect.

A radial air-cooled engine With. these and other objects in mind, as will appear hereafter, my invention comprises the novel joint, and the novel combination and arrangement of parts with respect to such joint, as

mounts are now almost universally used to absorb 5 shown in the accompanying drawing, and as will such vibrations and prevent their transmission to be described in this specification and more parthe aircraft structure. .In modern aircraft turboticularly defined by the claims which terminate superchargers of appreciable mass (wherefore the same.

they are mounted upon the relatively stationary In the accompanying drawing I have shown my aircraft structure) are driven from the pressure invention in conjunction with an engine, support,- of the exhaust gas from such engines. It .being framework and flexible engine mount of typhcomes necessary to provide a conduit with a fiexcal form, and I have shown the joint itself in ible joint between the oscillatably mounted engine various illustrative forms, each of which incorand the fixedly mounted turbo-supercharger. porates the principles of my invention, it being This joint, while subjected to intensely high temunderstood, however, that the form, arrangement, peratures, precluding any attempt at lubrication, andcharacteristics of a particular joint may be must still work freely under widely varying convaried in accordance with the principles of my ditions so that it will not appreciably damp vibrainvention, as may be desired for any particular tions in any direction, nor transmit them from installation or by any individual designer.

the engine to the aircraft structure, yet it must Figure 1 is an elevation with housing elements be sufliciently tight to avoid appreciable lessen broken away, illustrating such an installation in mg of the pressure of the exhaust ga's. This conjunction with anengine and enginemount, pressure at no time reaches a high value, and "andin conjunction withaturbo-supercha'rger. must be conserved and utilized to drive the ex- Figure 2 is an axial section through the joint haust gasturbine. Neither must such a joint be .itself, in a preferred form. restricted in area, for this would-increase back Figure 3 is a view similar to Figure 2, and Figpressure, and reduce usable pressure at the turure 4 is a similar view, each 'showing further bine. modifications of the joint. 5

My invention is not concerned with the engine Referring first to Figure 1, a conventional nor the engine mount per se, nor with the turboengine mount structure is indicated at 90, termisupercharger as such. 'My inventionis primarily nating in an engine mount ring 9|, from the concerned with, and has for its primary object latter of which, by means of flexible joints of any the provision of, a flexible joint having the suitable type, represented at 92, the engine 9 is capabilities indicated, for use in such an installasupported. These engine mounts 92 generally 1 tion. have the characteristic of permitting limited It is an important object of the present invenmovement fore'and aft, ,up and down, and tortion to provide a flexible joint which will be selfsionally, that is, in all directions. The engine is sealing, and. in which the force which tends to normally supported within a cowl ring 93, and its hold thejoint tight will be supplied primarily byrear or accessory section is housed within a cowlthe pressure of the exhaust gas itself, without 40 mg indicated at 9|, and suitably supported from dependence upon mechanical forces such as the framework 99, 9|. The latter framework is spring forces, to the end that the joint will always supported from the general airplane structure be held sufllciently but not unduly tight by a indicated at 95. force which varies in accordance with variations The engine cylinders discharge exhaust gas into an exhaust collector ring 80, which terminates" in a short exhaustpipe 8. These exhaust conduits vibrate with the engine whereon they are mounted. Aligned with but spaced from the exhaust pipe 8 is a tail pipe I which is fixedly mounted, by conventional means not shown, upon the structure or 95. Supplied with exhaust gas under'pressure from the tail pipe I may be such an element as the exhaust turbine 8 which in turn is connected to drive the supercharger 9|,

supplied with air by, means of an intake pipe 6,2,

all the latter structure is usually fixedly supported'from the main aircraft structure, or from the nacelle or the aircraft structure 85, the precise mounting varying in different installations and designs.

Between the exhaust pipe 8 and the axially aligned but rearwardly spaced tail pipe I is disposed the flexible joint which connects the two pipes, and which permits vibration-induced movement or oscillation of one with respect to the other. This joint is shown in detail in a preferred form in Figure 2.

The joint itself is very simply constructed of a plurality, preferably, two only, telescoping sleeves I and I8. These tubes slide telescopingly one within the other, along their common 'ain's, which is also the general common axis Y of the pin s- 8 and I, when the engine is at rest. When the engine is oscillating the axis of the pipe 8 may be displaced, for instance as is indicated at Y. The illustration may be somewhat exaggerated as to the degree of displacement, but a displacement of the axis of this nature occurs because of the oswards the two ends of the joint, and against the shoulders mentioned, to urge the joint ends apart. -Since their movement apart is resisted by the belled ends I6 and 86, it follows that the joints belled ends I I are pressed against the ends I6 and 86 by a force which for any given pressure is determined by the area chosen for the annular shoulder, and which in any given joint varies in accordance with the exhaust pressure. Thus it is the pressure of the exhaust gas itself which produces this force, and the force is directly proportional to the variation in the exhaust gas pressure. If the exhaust gas pressure rises and requires a tighter joint to contain it, the force acting to spread apart the sleeves I and I8 is thereby and correspondingly increased.

There is a further force acting to hold the joint tight, arising from the fact that the pressure, as the gas flows from the pipe 8 of given diameter into the joint of larger diameter, tends to build up in the joint by the reverse Venturi effect. The exhaust pressure P may rise, in flowing into the enlarged joint, to a value of P plus P. This prescillation permitted by the flexible engine mounts The outer end of each sleeve, or if there are more than two sleeves, the outer ends of the terminal sleeves, are belled, preferably spherically, as is indicated at II. If the oscillation were in a single plane or direction only, it would be unnecessary that the belling be spherical in nature,

but the oscillations of the engine normally have various components in various directions, and it is preferred that, the belling be spherical so that the joint may be universally flexible, to a limited extent at least. The matching ends of the pipes 8 and 'I are correspondingly belled, as is indicated at 86 and I6, respectively. The respective centers of these bells are represented at C1 and C2. The center 01 shifts its position with the shifting of the axis Y, but the center C2 is to all intents and purposes stationary. As a result the axis 3 of the joint itself moves angularly (somewhat conically) about C2 as a center, as is indicated in Figure 2. In so doing the joint may elongate slightly and contract, but the telescoping of the sleeves I and I8 accommodates this, while the angular movement is accommodated by the spherically belled ends II fitting within the re-, spectivematching belled ends 86 and 16.

The belled ends of the sleeves are normally urged apart, not so much by the springs 2 reacting between the lugs or ears 2| and 22 upon the respective sleeves I and I8, but by reason of the fact that the exhaust pressure itself, acting upon the sleeves I and I8," produces a force acting and reacting along the axis 3 towards each of the belled ends II.

The belling of the ends I I produces a shoulder, and locates the smallest diameter of the joint I, I8 at the juncture of the belled ends II with the matching bells 86 and I6. Inwardly of this smallest diameter, and inwardly of the shoulder thus defined, the joint sleeves I and I8 are of larger diameter. It follows that a given exhaust pressure P, acting within the conduits I and 8 and within the joint I, I8, acts within. the joint upon an area Al-in excess of the area whereon it acts within the conduits-represented by the annulus 'within the joint there is a static force acting tothe ends of the sleeves I and I8.

sure increment P acts, cumulatively with the aforesaid pressure P, to produce a total force (P+P)A, acting to hold the joint tight, and the total force varies in accordance with any variation of pressure difference as between the exhaust pressure and the atmospheric pressure.

It can be seen now that the springs 2 are provided merely to hold and to urge apart the sleeves I and I8 when no exhaust pressure is acting upon them. Were there no springsprovided the joint might under such conditions collapse or tend to cook, and the springs, which are light springs,

merely serve to hold the joint in proper shape,

with the parts in position. for use during such times as the engine isnot operating and there is no exhaust pressure within the exhaust conduit. Three or more such springs are normally provided, suitably distributed about the joint.

The principle of different diameters and of the resultant force tending to separate the sleeves.

the arrangement is substantially the same insofar as concerns the location of the centers Cl. and C2, but the-sleeves are enlarged to form the shoulder only within the telescoping portion, and then are restricted again, as indicated at I3, to substantially the same diameter at the juncture with the bells I6 and 86 as the pipes I and 8. The

outer ends of the sleeves are then outwardly, instead of inwardly, belled, as indicated at H.

In Figure 4 the arrangement is substantially similar to that of Figure. 3 except that the centers of the belling are indicated now at C: and C4, respectively, and are located along the axis Y, but within the pipes 8 and I, and therefore beyond It follows that the spheres of the bells are reversed; the sleeves have their end II" belled outwardly, both radially and alongthe axis, and the pipes having the respective belled ends 86' and I6 belled outwardly and backwardly, that is, 'backwardly towardthe respective pipes.

In all these forms, as will be apparent,,the smallest diameter of the terminal sleeves is at the juncture of their belied ends with. thebelled ends 16 and 86, and thediilerence of diameter as between the sleeves and the matching pipes affords a shoulder within the sleeves, facing outwardly of the joint, whereby the pressure effective on this shoulder (whether increased by the reverse Venturi eflect or not) reacts as between the two shoulders upon the two sleeves to tend to spread the sleeves apart, or to separate them,

that is, to force their belied ends into close fitting engagement with the belied matching ends oi the two pipes. This forms atight joint, yet one that will not unduly bind, and which is self adapting to variations in exhaust pressure.

While the preceding discussion has dwelt upon the use of the joint with a radial engine in an airplane it will be evident that other types of in an axial direction, but which are mounted for substantial relative bodily transverse movement, said joint including two telescoping sleeves, each having its outer end belied, and the respective matching pipe ends being disposed axially outrwardly of the sleeve ends, and being correspondingly belied to define a rodkable tight joint,-

' each sleeve being each interiorly formed with an excess'oi diametral inwardly facing area over diametrai outwardly facing area, thereby providing means upon which the internal fluid pressure acts to urge the sleeve ends outwardly into the I matching pipe ends.

2. A pressure-tight flexible joint 'iortransmission and. conservation of a pressure fluid between axially separated pipe ends which are independengines or instrumentalities are likewise subject I to vibration, perhaps different in kind or-degree, and are usually so mounted'that they may vibrate or oscillate (the terms as herein used are synonymous) relative to their supporting structure. An instrument may be shock-mounted upon its supporting panel, yet require supply or a fluid through a conduit, and it may be desirable to employ such a joint in such an installation. Likewise. engines of automobiles are subject to like vibrations, and are similarly mounted, and the principles of this invention are uselul in such 'in-. stallations. [The specific terms used herein are to be understood then as illustrative only, .not as restrictive, and to include the larger or-ge'neric sense, unless the context clearly indicates the contrary.

what I claim as my invention is:

' the center or the spherical beiling is located ale! 1. A pressure-tightvflexible joint for transniission and conservationpi a pressure fluid between axially separated pipe ends which are independently flxed against substantial relative movement the axis of the joint, and inside the ends of the sleeves.

4. A ioint as in claim 2, characterized in that the. center of the spherical beillng is located along the axis of each tube, and inside the ends oi the pipes. c .7

EDWARD C. WELIS. 

